Gordon Brown last night hailed the ­beginning of the end for tax havens, as Switzerland opened up its ­legendary system of bank secrecy and agreed to hand over information on wealthy clients suspected of tax evasion.

The move, described as historic by anti-poverty campaigners, came as ­international pressure, including action from Brown and Barack Obama, forced the world's tax havens to hand over previously undisclosed data on account holders.

Swiss ministers said the government caved in after learning the country was going to be included this month on a ­blacklist of uncooperative tax havens drawn up by the Organisation for ­Economic Co-operation and Development (OECD). Having agreed to sign up to the OECD protocol on tax, Switzerland will hand over information on account ­holders suspected of tax evasion by another country.

Until now tax evasion was not illegal in Switzerland and secrecy has been the bedrock of its economy.

Hans-Rudolf Merz, Swiss president and finance minister, said yesterday: "Co-operation on taxes has become more important given the globalisation of ­financial markets and in particular against the background of the financial crisis."

Switzerland is the world's biggest tax haven. The world's rich hide at least $1.89 tn (£1.35tn) of the estimated $7trn of ­private wealth there according to the Swiss Bankers Association, though others put the figure much higher.

Dr Andreas Missbach, joint managing director of Swiss anti-poverty campaign group Berne Declaration, said: "This is a major and historic first step. We have reason to celebrate but we still demand automatic exchange of information to address profound global economic imbalances."

The world's tax havens have been ­rattled by a series of events that have forced them to come into the open.

The Guardian has run a series of articles in its Tax Gap investigation detailing how some British companies use such havens to pay less tax to the UK treasury.

The global banking collapse revealed that many of the most complex debt instruments were based in offshore ­centres such as Jersey.

Obama has made cracking down on secretive jurisdictions central to his ­economic justice programme. ­

The fresh concessions by tax havens will not lead to full disclosure of the true ­beneficiaries of the complicated maze of sham trusts designed to confuse ­international tax authorities.

Campaign groups from all over Europe marched through Jersey's capital, St Helier yesterday. In a statement the aid groups demanded "a systemic change … to allow developing countries to get hold of the information they need … so they can stop the tax evasion".

The extent to which companies and individuals are using overseas tax havens to legally dodge tax has been exposed in the ­Tax Gap series. The investigation found that Royal Bank of Scotland used a series of schemes to avoid paying £500m to British and US revenues.